544 



SCANDINAVIAN FISHES. 



coloration (though also in form) and habits. Their ap- 

 pearance resembles that of the Mackerel or Sand-eel, 

 ■with a silvery lustre on the sides. The tii'st dorsal fin, 

 like the barbels, develops comparative!}- late; but the 

 ventral fins are long, though -with few i-ays and with 

 the outer part l)lack, in the early stages. The forepart 

 of the body and the head are laterally compressed, and 

 sometimes, according to LOtken, each of the temples is 

 furnished with t\vo spines. The eyes are as usual com- 

 parativelv lai'ge in these young specimens, which, how- 

 ever, possess the characteristics of the genus. During 

 the summer-months they live in companies or shoals 

 at the surface, and are often cast ashore or into the 

 fishing-boats by the Avaves. They are also eagerly de- 

 voured by sea-birds and fishes-of-prey. The older spe- 

 cimens keep to the bottom, leading a more solitary life 

 and hiding themselves under rocks, stones, and seaweed, 

 or roving about on the clayey bottom. The older spe- 

 cimens are remarkably tenacious of life, while the fry 

 die almost as soon as they are taken out of the water. 

 All these ditt'erences, which also vary in their duration, 

 one example of a species retaining a, juvenile character 

 longer than another, gave rise to the establishment of 

 a distinct genus, Couchia", to receive the young forms. 



an error which was first corrected by Malm* and sub- 

 sequently by Lutken". 



The genus Onos contains 10 known species'', one 

 from Japan, one from the south of the Indian Ocean, 

 seven from the Atlantic, the Arctic Ocean, and the 

 Mediteri'anean, and one from the ]\Iediterranean alone. 

 The species which belong to the Scandinavian fauna 

 may be distinguished as follows: 



A: Lono-itudinal diameter of the eves more 

 thau oO % of the postorbital length of 

 the head. A sino-le barbel at the verv 



tip of the snout < hios cimhrius. 



B: Longitudinal diameter of the eyes loss 

 than 30 "» of the postorbital length of 

 the head. 



a: Length of the head, even after the 

 Coucliia-stage, more than 23 > of that 

 of the body'. Margin of the snout 



furnished with several pairs of barbels Onos septentrionalis. 



b: Length of the head, after the Coucliia- 



stage,less than 23% of that of the body. 



a: Ijcngth of the lower jaw more 



than half that of the head. Tip 



and margin of the snout witliout 



barbels Onos tricirratus. 



(i: Length of the lower jaw less than 

 half that of the head. Tip of the 

 snout furnished with a pair of 

 barbels Onos niustela. 



THE FOUR-BEARDED ROCKLING (sw. fyrtommade skaklangan). 



ONOS CIMBRIUS. 



Plate XXVII, fig. 1. 



Four barbels: one at each of the anterior nostrils, one on the tip of the snout, and one on the chin. Length of 



the head in fuU-groirn specimens {after the Couchia-stage) less than 20 % {about 17 — 19 %) of that of the body. 



Longitudinal diameter of the eyes more than 30 % {about 32 — 40 %) of the postorbital length of the head, which 



is less than the distance between the tip of the snout and the hind extremity of the maxillary bones. 



Length of the h>u-er Jan- at least Vs {oO—(ll %>) of that of the head. 



R. hi: 7; D. 45 — 51^ A. 39—43!'; /'. 15 — 17; T'. 5— C; 

 a. 30—31; Vert. 52(67 '')• 

 S'l/n. Gadiis cimbrins, Lin., Syst. Nat., ed. XII, tom. I, p. 440; 



Stkussenfelt, Vet.-Akad. Handl. 1773, p. 22, tab. 2, fig. A; 



Bl. Schn. (Enchelyojnis cimhricus), Syst. Ichth., p. 50, tab. 



9; Retz. (Gadiis), Fii. Suec. Lin., p. 323; Nilss. (Motetla), 

 Frodr. Ichth. Sccnid., p. 48; ScHAGEnsTR., Physiogr. Sallsk. 

 Tidskr., p. 302; Parn., Mem. Wein. Nat. Hist. Soc, vol. VII, 

 p. 449, tab. XLIV; Kr., Daiiiii. Fiske, vol. II, p. 198; 

 Ekstr., Gbgg, Vet., Vitt. S.imh. Handl., Ny Tidsf., H. I, p. 



" Called Ciliata by Couch (Loud. Mag. Nat. Hist. vol. V, p. 16), and subsequently altered to Coiichia by TFiOMrsoN {A'at. Hist. Irel., 

 vol. IV, p. 190). 



'■ Skand. Naturf. M. Kblivn 1873, Der., p. 384; Gbgs, Boh. Fn., p. 495. 



<■ Vid. Meddel. Naturli. For. Kbhvn 1881, p. 239. 



<* Besides these GCnthek has described Onos macrophthaJmus (from 80 — 90 fathoms, off the Hebrides) and Onos Carpenteri (from 180 

 fathoms, between the Shetland and Faroe Islands), young, three-bearded Roeklings, of each of which only one single specimen is known. 



' III the Mediterranean, according to Moheau, Onos tricirratus may also possess this character. 



•' 53, according to Storer. 



48 



'' According to Malm. 



